Public Health Study: Proximity to Sprawl Affects Walkability

A scientific article just published in the American Journal of Preventive Medicine reports that a person’s proximity to Miami-Dade’s urban development boundary and central business district impacts walkability, and, by extension, has important health implications.

Distance (in miles) from the Urban Development Boundary in Miami–Dade County, Florida. Map Source: Matthew Toro. 2013. [Reprinted with copyright clearance permission of Elsevier, publisher of the American Journal of Preventive Medicine.]

As a reminder, the urban development boundary is a zoning tool that restricts certain types and densities of real estate development in the western and southern parts of the county, where ecologically-sensitive lands like the Everglades ecosystems, water conservation areas, and agricultural activities are located. (For more background on the UDB, read Miami Geographic’s“Meet the UDB” post.)

Agricultural Land-Use in Miami-Dade. Source: Matthew Toro. 2014.

As you move westward through Miami and approach the UDB, you’ll notice lower building densities, larger block sizes, a more disjointed street network, and a more monotonous land-use configuration, dominated especially by single-family (as opposed to multi-family) residential use.

Within the shopping center is a grocery store (Publix?), next to a pharmacy (CVS/Walgreens?), not too far from from a large gym (LA Fitness?), next to a health supplement store (GNC / Vitamin Shoppe?), a Starbucks coffee shop (no competition there), and some other assortment of storefronts typically occupied by large corporate entities.

Commercial Land-Use in Miami-Dade. Source: Matthew Toro. 2014.

Needless to say, within the Sea of Asphaltia, you’ll also invariably find a couple of nearby islands: perhaps a bank, a fast-food joint (e.g., McDonald’s, Burger King, Wendy’s, Taco Bell, etc.), and almost certainly a gas station or two.

This is nothing new, of course. We’re all well-acquainted with the geography of American suburbia, or, as Howard Kunslter describes it, the geography of nowhere.

The central business district, on the other hand, represents the urban geographical inverse of the UDB.

As you traverse the city in an eastward direction, you’ll notice a greater density of buildings, the size of blocks decreasing, better connected streets, more diversity in the types of land-uses, and, most importantly, you’ll notice more people out-and-about on the streets, on their very own two feet.

Distance (in miles) from the Central Business District in Miami–Dade County, Florida. Map Source: Matthew Toro. 2013. [Reprinted with copyright clearance permission of Elsevier, publisher of the American Journal of Preventive Medicine.]

(Full disclosure: I am a proud member of this research team and co-author on the study. All views expressed here in Miami Geographic are, of course, my own and not to be associated with any other person or entity.)

The intention was to determine whether people living nearer to Miami’s periphery exhibited any differences in walking behaviors from those who lived nearer to Miami’s core.

Address data from 391 Cuban-immigrant study participants were geocoded to map-out the distribution of where they lived throughout Miami-Dade County.

Distances were then calculated from each of the participants’ homes to (1) the urban development boundary, and (2) the central business district.

After controlling for multiple socio-demographic/socio-economic variables, the team found that people who lived farther from the UDB were likely to walk more than those who lived nearer to the UDB.

Each one-mile increase in distance from the UDB corresponded to an 11% increase in the number of minutes of purposive walking.

That’s right: More than two-thirds of our county population is obese or overweight.

Maybe the easiest and most effective way to counter the growing obesity epidemic in Miami at the public policy level is to redirect the typical Miami model of development away from sprawling suburbs eager to encroach upon our most critical natural and agricultural resources.

Perhaps Dr. Claudia Miller, physician and assistant dean at the University of Texas School of Medicine, was right when she provocatively commented that, “Architects have a greater ability to improve public health than medical professionals.”

I think it would be interesting to see a heat map similar to the “Distance from UDB” map there, but for “walk likelihood” and/or health outcomes. It is hard to believe that it would look exactly the same, but seeing how close it is would be very informative.